The invention relates to a control jack for a knitting machine having at least one selector device for knitting implements. The jack comprises: a front side and a rear side, first and second lever arms arranged on opposite sides of a bearing point, wherein the first lever arm has an armature surface and the second lever arm has a rocking butt, a spring arranged on the rear side for biasing the second lever arm and a controllable raising butt, wherein the controllable raising butt, the rocking butt and the armature surface are formed on the front side.
In order to implement the so-called three-path technique, i.e. an arbitrary selection of all knitting needles for knit, tuck and miss at a knitting system, numerous pattern devices are already known. These consist essentially of cam system parts forming knit, tuck and miss tracks and mechanical, electronic or electromagnetic control means, by means of which the knitting implements are distribute to these tracks.
In most knitting machines which arc already known, which are designed for a three path technique, either a substantial increase in the system width and/or a comparatively expensive construction of the pattern devices or the associated needles or jack has to be accepted. Thus for example a knitting machine is known (DE 3 739 924 A1) in which the control jacks associated with the knitting needles firstly have to be distributed at a first selector station in accordance with a pattern to a miss track and to a cam system track leading to the tuck position and then in a second selector station be left in accordance with the pattern in the tuck track or diverted into a knit track. Against the advantage that knitting needles and control jacks well-tried in practice can be used, there is the disadvantage that the double selection involves substantially doubling the system width, which means a large loss in performance on account of the small number of systems in any case possible, e.g. 48 systems with a needle cylinder diameter of 30". This disadvantage can indeed be avoided by a likewise known circular knitting machine (DE 4 007253 C2), with makes the three-path technique possible without substantial system widening compared with the usual two-path technique. However such a knitting machine requires the use of special knitting needles with at least two pivotable control butts each instead of the generally used latch or slide needles, which is undesirable for reasons of cost.
Similar problems have arisen in the attempts to make other known selector devices previously used only for the two-path technique usable for the three-path technique. This applies for example to known selector devices (DE 3 712 673 C1) in which control jacks in the form of single arm levers are associated with the knitting needles and serve simultaneously as control elements and needle push-jacks. These control jacks are biased radially outwards by springs fitted in their backs, into a raise position and have to be swung on to the control magnet, which lie-s radially inside the needle circle, against the spring force before reaching the selection station, by means of a special presser race, which acts on rocking butts of the control jacks, in order thereby to lower the controllable raising butts into the needle tricks, i.e. swing them out into the working range of the cam system races. If such a selector device is used to make a double selection station, in that for example a second, corresponding selector device is arranged where the needles reach the tack position, a second presser cam system part must be associated with this second selector device, in order to swing the control jacks running in the tuck position away from the corresponding raise part and apply them to a second control magnet. This second presser cam system part does indeed not double the system width as in the first cited knitting machines, but has the result that in no case can 60, 64 or 72 systems be fitted round the periphery of a circular knitting machine with a needle cylinder diameter of 30", which is desirable for patterning reasons. In still further known knitting machines of this kind (DE-AS 1 760 405), which are also provided with control jacks in the form of single arm levers, each having a controllable raising butt, there is indeed the advantage that these already assume a position on reaching the tuck position which makes the use of a presser cam system part for the second control magnet unnecessary. A disadvantage with this solution is however the fact that the control jacks either each have to be provided on both sides with a spring or when using only one spring disposed on the front side of the control jacks, an additional tensioning cam system, part is needed for this, which results in a corresponding unfavourable system widening as does a presser cam system part for the control jacks.
Finally a knitting machine of the type initially recited has already been made known (DE 3 541 171 C2), in which the control jack is formed as a two-armed lever, where the one lever arm comprises the armature surface for the control magnet and the other lover arm comprises a rocking butt cooperating with a presser cam system part and a controllable raising butt cooperating with raise races. The control magnet is located in this case on the front side of the control jacks. The pattern device developed as a whole for the particular case of a flat knitting machine is of comparatively complex construction. The control jacks serve only as control elements but not as needle push-jacks. Only a pre-selection is effected by them and the control magnet while the transfer of the needles into the tuck or knit position is effected with other means and at a location lying after the double selector station. The double selection is here effected in that all control jacks are applied to the control magnet at the first selector station by means of a presser cam, in order to select and thus raise first control jacks by pattern-based control of the control magnet, while the other control jacks are held deflected by an associated retaining pole against the forces of the springs, until they reach the second selector station, where selection or raising of second control jacks takes place, while all other control jacks remain in a pass position. The controllable raising butts in each case effect only a comparatively short lift of the control jacks, while the actual separation of the control jacks selected to knit, tuck and miss, i.e. of the knitting needles associated therewith is effected in each case by means of an additionally present, second, non-controllable raising butt, which is formed on the lever arm of each control jack with the armature surface and always assumes a raise position regardless of the position of the controllable raising butt, as well as additional needle lifters which can likewise pivot.
Such a selector device accordingly does not only involve a substantial increase in the system width and in the expense of construction but also does not operate with sufficient reliability, at least when used on circular knitting machines, Since the control jacks are held tight between the two selector stations solely by the holding magnet, it is not possible reliably to avoid the control jacks dropping uncontrollably off the hold magnet because of the action of the springs, therefore causing pattern faults, when vibration unavoidably occurs in rapidly running circular knitting machines.